This disclosure relates generally to systems for detecting the position of an item. More particularly, the present disclosure relates to a method and a system for using Radio Frequency Identification (RFID) tags to determine the position of an item.
There are many contexts in which it is useful or even necessary to know the position of an item in the physical world. For example, logistics systems need to track the movements of goods through warehouses, and assembly robots need to determine the position of cars as they move down the assembly line. Applications of such knowledge are nearly countless, because knowing the position of objects is a fundamental requirement for interacting with the physical world.
One technique for determining the position of a physical object is to modify the object to so that it is able to track its own position, and to report its position through a wired or wireless connection. While this technique is useful for some applications, it does not lend itself to all such applications. The tracking apparatus may be bulkier than the item that is being tracked, thereby making it difficult or impossible to use in the particular environment in which the object may be located. The item or the tracking apparatus must contain a wireless communications system and a power supply, which further increases bulk, or be tethered through a physical connection. Moreover, it is expensive to modify an object in this way.
Another technique is to use a video camera to survey a scene, and to use object recognition software to identify and determine the location of objects within the scene. However, this technique is expensive and requires line of sight access to the camera.
A relatively inexpensive technique for determining the position of an object in the physical world is to attach a Radio Frequency Identification (RFID) tag to the object. RFID tags are relatively small, relatively inexpensive, and passive RFID tags do not require a power source. Each RFID tag has a unique identifier that can be read wirelessly by RFID tag readers. RFID tag readers do not require a direct line of sight to tags to be able to read them and typically has a range of few feet for the most popular and inexpensive passive tags. However, typical RFID tag readers cannot pinpoint the exact location of the object. Rather, they simply report the presence or absence of a tag in their field of sensitivity.
Conventionally, if an item having an RFID tag is to be located, the RFID tag reader would have to be transported around the area in which the item is thought to be in order to find the item. Alternatively, the area would be divided in sections, with each section having an RFID tag reader. The sections are sized such that any item within the area is always within range of one of the RFID tag readers. The problem with this method is that RFID tag readers are much more expensive than RFID tags, making this method for an expensive solution to implement, particularly for large archives.
Another problem with both of these conventional methods is that they assume that the user is familiar with the distribution of sections in the area. So even if the general location is known, for example the item is located in section H7, the user would still need to find where the section H7 is in the area. This is especially difficult for large areas/archives or archives that do not follow a simple way of classifying the sections. Further, even after the user finds the section of the area/archive that contains the item, he or she must still perform a sequential search in that section to locate the item. This is a time consuming operation for archives divided in large sections.